In HDR imaging, a dynamic range generally refers to a range of a plurality of independent, different lighting, exposure or brightness levels that are used to create respective images (or image information data sets) of a particular scene, wherein the different images/data are combined or otherwise used together to create a single HDR image, for example through use of software applications. This allows overexposed areas or underexposed areas in any given picture region in any given image to be replaced by image data from another image taken at a different level of light exposure, thereby generating an image over a range of the different lighting, exposure or brightness levels.
Photographic images with different lighting, exposure or brightness levels are conventionally obtained through varying the respective focal-stop (“f-stop”) values of the lens aperture of a camera used to acquire each of the images. The f-stop value is the focal length of the lens divided by the diameter of its opening, and is conventionally chosen from a graduated scale wherein each consecutive f-stop halves the opening of the previous value, and thus lower f-stop values admit more light through the lens to an image sensor, for example film material in analog photography, or charge-coupled device (CCD) or composite metal oxide semiconductor (CMOS) sensor devices in digital photography. In one example an 80 mm lens with an f-stop set to f8 has an opening diameter equivalent to 10 mm, wherein changing the f-stop to f16 creates a diameter of 5 mm. However, the f-stop setting may also determine the “depth of field” of the acquired image data; how much of image in front of and behind a subject in focus will also be in focus, with smaller f-stops providing images with relatively larger depths of field as compared to images acquired by the same lens at larger f-stop settings. Therefore, varying admitted light levels through varying f-stop settings of a lens to acquire multiple images of a scene for HDR present many problems; such images may have different respective depths of field, with some foreground and background elements out-of-focus in the larger f-stop images.